Arrangement for varying wave lengths in coaxial lines



y 1952 M. G. WHITE 2,604,594

ARRANGEMENT FOR VARYING WAVE LENGTHS IN COAXIAL LINES Original Filed Oct. 2, 1943 FIG.2

INVENTOR MILTON G. WHITE BY WE-W ATTORNEY Patented July 22, 1952 UNITED STATES PATENT I" V 2,604,594., 1".

ARRANGEMENT FOR VABYING WAVE 7 f unnnqrns IN eoAxIAL LINES V 4, Milton" white; Cambridge, Mass, assignor, by

' America mesne assignments, to theUnited States of i 7 as represented by the Secretary of the Original application October 2, 1943, Serial No.

- 504,777. Divided and this ber 14, 1,9 Serial No. 616,397

paratus. The invention is applicable both to 5 coaxial-conductor wave guides and to hollowpipe wave guides and concerns control of the wave 'length oi traveling waves of a given ireque'ncy within such wave guides. This application-is a division of my application Serial 504,777, filed October2, 1943, and entitled Control of Wave "Lengths in Wave; Guides, nQWPatent No.

2,567,748 grantedSeptember 1. 1951.

" l ormany purposes it is desirable to modify the wave length. Sometimes, in addition to shortening-,thewave lengths, it is even desired to provide arrangements for varying, periodically or otherwise, the wavelength of the oscillations in t e W de m l o t mne'foi. th wa length can .be accomplished"loy substituting solid dielectric material for the otherwise more. convenient air insulatiombut this method of s'hortening the wave length has certain disadvantages.

If the dielectric material extends completely across the wave guideor evenjacross'alarge por- Q'tionof the wave guidethe accumulation ofmoisture or dirt "on the surface'sj'of the' various pieces of dielectric material'involvesjan electrical breakdown hazard which is particularly "serious on "account of the fact that if a. breakdown'should cccur, the dielectric, if itof organic'mate'rial asin the case of the dielectricswith the most desirable electrical qualities, will be carbonized and precipitate apermanent failure or at least a source of losses, andjin some cases the dielectric may actually catch fire. Also, when the, wave guide is filled or almost filled with solid dielectric material it becomes very difficult tov provide arrangetransmission of application sem n.

. wave guides, in which the'wave length of electric ments for varying the wave length in the wave guide forte. given'frequency' overiany substantial range of wave lengths. v

It is an object of the present invention to provide for shortening the wave lengthin wave guide structures by. the provision .of suitable'structures in'said wave guides. .11; is a'i'urtherobj'ect'of this invention to provide such wave length shortening without the use of solid dielectric material in any, location of .high electric stressarid, the general case/Without thenecessity .of any solid dielectric. material .at. all. I ;Itis a further object of this, invention to provide means ;forvarying at will within a substantiallrange the wave length of electric oscillations in. a wave v guide"fwi tl'iout varyingthe frequency; thereof. Z'It is a-liurther object of the invention to provide a certain adoscillations is controlled as" aforesaid. Still a further object of the invention is to provide wave guides with shortened wave lengthcharacteristics with respect to wavestransmitted therein which exhibit such characteristics in connection-width the transmission of. traveling waves under'conditions of good energy. transfer and lowlintern al reflection and even in the substantial ab'senceof standing waves. v v

' In accordance with thepresent invention, certain repeated obstructions relatively closed spaced in terms of the wave length are introduced or constructed in a wave guide, which so affect the field, as further explained below, that the wave length is shortened. A number of forms of such arrangements are possible' and it is also possible to provide means for mechanically moving certain of the obstructions whichmeans are capable of producing a variation in the shortening. of the Wave length, which is to say a variation in the wave length for a given frequency. The invention will be more fully explained in connection with the accompanying drawing in which:

Fig. 1 is a longitudinal cross sectionof a form of wave guide constructed-in accordance with the present invention adapted for variation of the wave length of oscillations in the wave guide; and

Fig. 2 is a general view and Fig. 3 is a detail of a form of antenna system making use of the present invention.

In Fig. 1 there is shown a coaxial-conductor wave guide in which the inner conductor is provided with ridges and grooves, the ridges. and grooves being in the form of a continuous screw thread. The outer conductor of the wave guide shown in Fig. 1 is provided with spaced projections 40.. These projections may be in a longitudinal row or in several staggered longitudinal rows, the projections being spaced by thev spacing between turns of thescrew thread on the inner conductor 38. If desired, the projections ofthe outer conductor 39 might also be provided. in the coalesced form of a continuous screw thread, but because of the difliculty 'ofpreparing such a structureit is preferred to provide a row of obstructions, which might be regarded as a discontinuous s'crew thread, and which may be conveniently mortised into, the outer conductor 39. Means may then be provided, v(not shown) for rotating the inner conductor 38 on its axis, with the result that the configuration of the electric field of the transmitted oscillations may be made' to vary according to the rotational position of the ,tervals on one side.

inner conductor 38. It is found that such variation results in variation of the wave length of oscillations of a given frequency transmitted in the wave guide. ,7 The, wave length is shortest when the screw'thread ridges on the inner con}- ductor 38" are substantially in registry with the projections 40 and becomes less short as the said.-

ridges and the said projections are displaced with {effective directional antenna characteristics from respect to each other. H which accompanies the relative shift of the ridges The wave length change? of the inner conductor past the projections on, the outer conductor in the' apparatusof.1j'ig.- 1

may be explained by considering that as the ridges and projections move into registry, the

electric field between them is intensified because of the increased localized capacitance, which intensification of charge is probably accompanied by increased activity of the field in the grooves between the various ridges and projections; thus intensifying the wave-length shortening efiect of these said grooves the same frequency in free space.

4 cerning the orientation of the directivity pattern of the antenna system.

By virtue of the wave-length-shortening effect provided in accordancewith this invention, the wave-length'in the gwave; guide I01 will be shorter than the wave lengths of oscillations of This condition is a practical necessity for the production of a series of slots such as the slots I02 and I03, because if the wavelength in the wave guide I01 were the same. or larger than the wave length in, free space there would be interference from higher order beams or. lobes which would form part "of the directivity characteristic of the sys- .tem. When the; wave length in the guide I01 1 is such' that the slots are spaced by the wave length in the guide, the maximum radiation will I00 and .an inner conductor IN, the outer conductor I00 having transverse slots at spaced in- If desired, the transverse slots-may be approximately a half-Wave length long, thus acting as "magnetic dipoles. I.Two such slots are shown at I02 and 103m Fig. 3. The inner conductor IOI isprovided witha radial projection in the form of a screw thread I04, substantially as shown with respect to the inner conductor 38 of Fig. 1. On the inner side of the outer conductor' l00 are-provided. certain projections I05 adapted-to cooperate with the screw thread I-M-and the inner cnductor I0! to provide a variable shortening of the wave length as the inner conductor IOI is rotated, again as described in connection with Fig. 1..

The slotted modified coaxial conductor wave guide shown in Fig. 3 maybe mounted, as shown in Fig. 2, on the side of the fuselage of an airplane. -The coaxial-waveguide, shownv at I0! is mounted clear of the fuselage, and the fuselage shown generally at I08, is providedwith a reflector I 00 in the form of a cylindrical paraboloid mounted in the fuselage wall and facing the wave guide I0! which lies in its focal axis, so that the reflector I09 is adapted to provide a certain amount of vertical concentration of the directional characteristics of the'slotted wave guide I01. The Wave guide I0! is so oriented that the slots are directed toward the reflector I09. Means (not shown) are provided for exciting the wave guide I0! at its left-hand (forward) end and for connecting the wave guide I0! with a suitable transmitter receiver apparatus (not shown). Absorbing material shown generally at II01is provided in the right-hand end of the wave guide I01 to absorb such power as is not radiated from the antenna during trans-.

the radio system (not shown) information con- 5 V be in a direction normal'to the axis of the guide. If the slotted portion of the guide is of substantial length, an extremely sharp beam may be produced (sharpness being in a plane substantially perpendicular to the axis of theguide, the

beam being sent out in such a plane). The

-phase and standing waves of fairly high amplitude exist in the wave guide I01. This condition, .however, exists only for a relatively narrow range of values of wave length in the guide in the neighborhood of that just mentioned, so that this phenomenon may actually be used to calibrate continuously. the apparatus used, in order to indicate accurately the position of the directive maximum of the antenna system, asnoted in the application of. L. W. Alvarez, Serial No. 509,790, filed November 10, 1943. d It is generally desirable to operate the apparatus in a range over which the spacing between the slots remains less than a wave length in the guide, or possibly reaches equality with a wave length in the guide, only at'the extreme portion of the cycle for purposes of check or calibration. If it is desired to center the sweep of the directive characteristics of the antenna system upon the direction perpendicular'to the axis of the airplane, the wave guide I 01 .may be arranged at a small angle to the axis of the airplane, which is quite feasible since the fuselage I08 will nor mally be narrower towards the rear of the airplane. In general an apparatus such as that shown in Fig. 2 will be mounted on each side of the airplane fuselage and the apparatus will be used for such purposes as detecting the presence of vessels at sea at long distances from a patrolling aircraft, thus greatly extending the area covered by the patrol. Other apparatus of known types could be used on the aircraft for detecting vessels nearer to the course of the patrolling craft.

' Various other ways of applying the principles of the present invention. for shortening the wave length of i'oscillations of a, given frequency in waveguides of various types and/or for'providing adjustability or variability of the wave length in such wave guides for a given frequency of operation are possible within the spirit of the by the appended claims. It is to be understood that dielectric material may be inserted between the projections of one or both conductors to increase the wave shortening effect as is done in certain embodiments of the parent application.

References to wave length made herein are intended to refer to desired frequencies of operation, at which it is intended that radio-frequency power should be transferred through the wave guide or guides in question. Unless otherwise specified, wave length dimensions refer to the wave length in the particular structure or environment under consideration.

What is claimed is: I

1. A coaxial wave guide antenna having inner and outer conductors and having on one of said conductors a plurality of spaced radial projections extending into the space between said conductors and having on the other of said conductors a continuous screw thread also extending into said space.

2. A coaxial wave guide antenna having inner and outer conductors and having on one of said conductors a, plurality of spaced radial projections extending into the space between said conductors and having on the other of said conductors a continuous screw thread, also extending into said space, the spacing between adjacent threads being substantially the same as the spacing between adjacent projections.

3. A coaxial wave guide antenna having inner and outer conductors and having on one of said conductors a plurality of spaced radial projections extending into the space between said conductors and having on the other of said conductors a continuous screw thread also extending into said space, said projections on at least one of said coaxial conductors being spaced so that there are more than two of said projections per wave length.

4. A coaxial wave guide antenna having inner and outer conductors and having on one of said conductors a plurality of spaced radial projections extending into the space between said conductors and having on the other of said conductors a continuous screw thread also extending into said space, said inner and outer conductors being rotatable with respect to each other whereby the wave length of oscillations of a given frequency may be varied.

5. A coaxial wave guide antenna having inner and outer conductors and having on one of said conductors a plurality of spaced radial projections extending into the space between said conductors and having on the other of said conductors a continuous screw thread also extending into said space, the spacing between adjacent threads being substantially the same as the spacing between adjacent projection and less than a half wave length, and said inner and outer conductors being rotatable with respect to each other whereby the wave length of oscillations of a given frequency may be varied.

6.v A coaxial wave guide having inner and outer conductors and having radial projections on one of said conductors and a helical projection on the other of said conductors.

7. Apparatus in accordance with claim 3. wherein said outer conductor is formed with a plurality of spaced transverse slots.

8. Apparatus in accordance with claim 5. wherein said outer conductor is formed with a plurality of spaced transverse slots.

9. A coaxial Wave guide antenna comprising inner and outer conductors, one of said conductors being rotatably mounted relative to the other of said conductors, said outer conductor being formed with a plurality of slots, spaced radial projections on one of said conductors, angularly disposed projections on the other of said conductors and means for rotating said rotatably mounted conductor.

10. A coaxial wave guide antenna having inner and outer conductors and having on one of said conductors a plurality of spaced radial projections extending into the space between said conductors and having on the other of said conductors a continuous screw thread also extending into said space, the spacing between adjacent threads being the same as the spacing between adjacent projections and less than a half wave length, one of said conductors being rotatably mounted relative to the other conductor, said outer conductor being formed with a plurality of spaced transverse'slots, and means for rotating said rotatably mounted conductor.

11. A wave guide comprising a hollow first conductor and a second conductor, disposed inside said first conductor in spaced relationship thereto, said conductors being mounted for relative movement such that the longitudinal axes of said two conductors maintain fixed relative positions, one of said conductors being provided with a plurality of transverse radial projections, the other of said two conductors being provided with at least one radial projection disposed at an angle to a transverse plane of said wave guide, said projections on said two conductors extending into the space between said two conductors.

MILTON G. WHITE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Datev 2,206,923 Southworth July 9, 1940 2,226,479 Pupp Dec. 24, 1940 2,338,441 Kohl Jan. 4, 1944 2,405,437 Leeds Aug. 6, 1946 2,408,435 Mason Oct. 1, 1946 2,433,368 Johnson et a1. Dec. 30, 1947 2,438,367 Keister Mar. 23, 1948 2,438,913 Hansen Apr. 6, 1948 2,460,109 Southworth Jan. 25, 1949 

